Yamaha F50LB Specifications
| Engine Model: Yamaha F50LB |
| Engine Type: 4-stroke inline 4-cylinder SOHC 8-valve gasoline outboard engine |
| Total Displacement: 60.8 cu.in (996 cc) |
| Rated Engine Power: 50 Hp (36.8 kW) at 5500 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
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The Yamaha F50LB is a 50-horsepower,
four-stroke, in-line four-cylinder outboard engine, representing a
benchmark of refinement and technology in Yamaha's mid-range lineup.
This model is configured for remote control operation and is equipped
with electric starting and a hydraulic power trim and tilt system,
offering boaters a sophisticated, powerful, and exceptionally smooth
experience.
Built on an advanced 996cc platform, the F50LB is renowned for its quiet
operation, outstanding fuel efficiency, and the seamless response of its
Electronic Fuel Injection system, making it a versatile and dependable
choice for a wide array of mid-sized boats.
The Yamaha F50LB is constructed around a refined and efficient
powerhead. It features a 4-stroke, SOHC, in-line 4-cylinder, 8-valve
engine configuration. The engine displacement is precisely 996 cc (60.8
cu in), achieved through a bore and stroke of 65.0 mm x 75.0 mm (2.56 in
x 2.95 in).
This powerhead produces a maximum prop shaft output of 36.8 kW (50 hp)
at 5,500 rpm. The engine is engineered to operate within a full throttle
operating range of 5,000 to 6,000 rpm, with a specified engine idle
speed of 700-800 rpm. The compression ratio is stated as 9.5:1.
The power unit of the F50LB is engineered for durability, efficiency,
and smooth power delivery. The 1.0 litre, eight-valve, single-overhead
camshaft, four-cylinder, long stroke design delivers ultra-smooth,
usable power with low noise and vibration levels.
The engine's long intake manifold and increased piston stroke contribute
to a broad, flat torque curve and impressive acceleration. The valve
train requires periodic adjustment, with specified valve clearances of
0.15-0.25 mm (0.006-0.010 in) for the intake valves and 0.25-0.35 mm
(0.010-0.014 in) for the exhaust valves when the engine is cold.
The F50LB features Yamaha's advanced Electronic Fuel Injection (EFI)
system, which precisely meters fuel for optimal combustion under all
conditions. The Multi-Point Electronic Fuel Injection (EFI) system
injects the right amount of fuel into the combustion chamber at the
optimum timing, taking into account engine speed and load requirements
to achieve maximum engine performance including first-time, every-time
hot and cold starting.
Air flow is precisely delivered to all four cylinders through a large
single throttle valve based on the demands of the driver and combustion
conditions, and is pulse-tuned before it reaches the injectors to
promote a clean and efficient burn for maximum economy and power. The
recommended fuel is regular unleaded gasoline with a minimum octane
rating of 87.
The lubrication system is a wet sump type, meaning the engine oil is
stored in a sump within the engine. The recommended engine oil is
high-quality 4-stroke outboard motor oil, such as Yamalube 4M, in SAE
10W-30 or 10W-40 viscosities, meeting API SE, SF, SG, SH, SJ, or SL
service classifications. The engine oil capacity is 2.5 L (2.6 US qt).
The cooling system is raw-water with thermostatic control, drawing water
from the body of water to cool the engine. A freshwater flushing system
is integrated for easy maintenance, allowing connection of a hose to
flush salt and dirt from the outboard without having to run the engine.
The exhaust system utilizes Yamaha's proven labyrinth exhaust system
which reduces engine noise at low RPM and idle, with a water sealed
outer wall around the exhaust muffler effectively reducing exhaust tone
for whisper quiet operation and enhancing cooling to protect against
corrosion. Exhaust gases are expelled through the propeller boss for
efficient underwater exhaust.
The ignition system is a TCI (Transistor Controlled Ignition)
microcomputer unit, providing precise spark timing for reliable starting
and efficient power across the RPM range. The system includes the Prime
Start feature for effortless cold starts, eliminating the need for a
conventional choke and allowing the engine to be started cold by
automatically controlling the engine warming up process.
The specified spark plugs are NGK DPR6EB-9, with a required gap of
0.8-0.9 mm (0.031-0.035 in). The charging system incorporates a
high-output alternator of 12V - 16A with a built-in rectifier/regulator
to maintain battery charge for the electric start and other electrical
accessories, with alternator output at WOT reaching 17A.
| Mid Section and Lower Unit |
The lower unit is engineered for strength and efficiency. It uses a
spiral bevel gear with a reduction gear ratio of 1.85:1 (24/13). The
gear shift positions are the standard Forward-Neutral-Reverse (F-N-R),
engaged via a positive-action dog clutch.
The propeller shaft utilizes a spline drive system, and the propeller
direction, when viewed from the rear, is clockwise or right hand
standard. The correct lubricant for the lower unit is hypoid gear oil
meeting API GL-4 SAE 90 specifications, with a gear oil capacity of 0.43
L (0.45 US qt).
This outboard is equipped with a hydraulic power trim and tilt system,
allowing for effortless adjustment of the engine angle with the touch of
a button across a wide trim range. Negative trim settings allow for
improved acceleration and the ability to bring the boat onto the plane
more quickly.
For shallow water operation, the system provides a standard shallow
water drive feature, allowing the engine to be operated at a tilted
angle for safe navigation. The steering angle is 40 degrees to both port
and starboard.
The Yamaha F50LB is compatible with a range of aluminum propellers to
match various boat types and applications. Performance testing on an
Alumacraft MV1756SC utilized a 11-5/8 x 11 aluminum propeller (Yamaha
part 69W-45947-00-00). Similar testing on a G3 Boats Outfitter V167 T
also used an 11 5/8 x 11 aluminum propeller.
Authorized Yamaha dealers can recommend the correct propeller based on
boat hull, load, and intended use to ensure the engine operates within
its recommended full-throttle RPM range of 5,000-6,000 rpm. The
propeller drive system utilizes a spline connection and propeller is
optional equipment.
The Yamaha F50LB is available in a long shaft configuration. The overall
length is 698 mm (27.5 in) and the overall width is 386 mm (15.2 in).
The overall height is 1,435 mm (56.5 in) with a transom height of 527 mm
(20.7 in). The dry weight for this model is 113 kg (249 lb).
Regular maintenance is essential for the longevity of the F50LB. The
engine oil and oil filter should be changed according to the
manufacturer's schedule. The gear oil in the lower unit should be
checked regularly for the presence of water or metal particles and
changed annually or every 100 hours. The water pump impeller is a wear
item that should be inspected and replaced periodically, every 1-2 years
or if there are signs of reduced cooling water flow, to prevent
overheating.
The spark plugs should be removed, inspected, cleaned, and the gap
adjusted annually, and replaced as needed. Valve clearance inspection
and adjustment should be performed at recommended intervals. All moving
parts, such as steering linkages and tilt tube, require regular greasing
with water-resistant marine grease to prevent corrosion and ensure
smooth operation.
The Enhanced Ultimate Corrosion Protection System (UCP) is a standard
feature for long-term durability. Yamaha's variable trolling control
allows precise adjustment of the engine's idling speed from 650 to 900
RPM in 50 RPM increments via the optional Command Link System, allowing
fishermen to perfect their lure presentation. An optional Y-COP engine
immobiliser system is available for enhanced security.
Spark plug: 18 Nm (13.5 lb-ft)
Propeller nut: 35 Nm (25 lb-ft)
Oil drain plug: 28 Nm (21 lb-ft)
Oil filter: 18 Nm (13.5 lb-ft)
The Yamaha F50LB is a versatile power source ideally suited for a wide
range of mid-sized watercraft up to approximately 5 meters in length.
Its 50-horsepower output, combined with the convenience of electric
start, EFI, and power trim and tilt, makes it a perfect match for
aluminum fishing boats such as the Alumacraft MV1756SC and G3 Boats
Outfitter V167 T, as well as center consoles, bay boats, and utility
boats commonly used on inland lakes and coastal waters.
It is also specified as power for boats like the Xpress Xplorer Bass
XP170. The four-stroke technology provides exceptionally clean and quiet
operation, making it suitable for various recreational applications
including fishing, touring, and family outings. The engine is available
with an optional tiller handle kit for those preferring tiller-steer
operation.
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